Input/output feedback linearization control of a three-phase three-level neutral point clamped boost rectifier

In this paper, the authors propose a new control strategy for a three-phase three-level neutral-point-clamped boost rectifier. It consists of applying a nonlinear feedback linearization technique. The nonlinear state space model of the rectifier was obtained in the (d,q,0) reference frame using the power balance between the input and output sides. The input/output feedback linearization is then applied and a linearizing control law is derived. Hence, the resulting model is linearized and decoupled. Afterwards, the tracking controllers are designed based on linear techniques to control line-currents, output and neutral point voltages. An integral action was added in order to robustify the controller with respect to parameter variations. This control uses a 3 kHz pulse width modulator. Computer simulations based on the use of Power System Blockset and Simulink/Matlab verify the robustness of the proposed control law in both balanced and unbalanced output load conditions. The line-current THD and output voltage ripples are very low. The settling time and the overshoot are quite small in comparison with standard PI controller.